In xcode, there are several methods for batch modifying variable names, file names, class names, protocol names, and so on.

Keyboard Shortcut

Select or position the mouse over the variable name you want to modify. Keyboard Shortcut Control - Command - E 

Xcode automatically highlights these variables. This is the shortcut for Edit All in Scope.

Menu

Select or position the mouse to the variable name, interface name, implementation name, or protocol name that you want to modify, and select the menu Editor -> Refator -> Rename. The editor will display a preview of the changes, including the project's code, file name, and comment content. Click Rename in the upper right corner to batch rename.